cleaned up some tests

Additionally, remove unused `tests/ui/auxiliary/svh-*` crates that are duplicates of `tests/ui/svh/auxiliary/svh-*`.

tests/ui/cast/cast-enum-to-primitive-error.fixed

@@ -1,5 +1,10 @@
+//! This test verifies that a direct non-primitive cast from an enum to an integer type
+//! is correctly disallowed, even when a `From` implementation exists for that enum.
+
 //@ run-rustfix
+
 #![allow(dead_code, unused_variables)]
+
 enum NonNullary {
     Nullary,
     Other(isize),
@@ -16,5 +21,7 @@ impl From<NonNullary> for isize {
 
 fn main() {
     let v = NonNullary::Nullary;
-    let val = isize::from(v); //~ ERROR non-primitive cast: `NonNullary` as `isize` [E0605]
+    let val = isize::from(v);
+    //~^ ERROR non-primitive cast: `NonNullary` as `isize` [E0605]
+    //~| HELP consider using the `From` trait instead
 }

tests/ui/cast/cast-enum-to-primitive-error.rs

@@ -1,5 +1,10 @@
+//! This test verifies that a direct non-primitive cast from an enum to an integer type
+//! is correctly disallowed, even when a `From` implementation exists for that enum.
+
 //@ run-rustfix
+
 #![allow(dead_code, unused_variables)]
+
 enum NonNullary {
     Nullary,
     Other(isize),
@@ -16,5 +21,7 @@ impl From<NonNullary> for isize {
 
 fn main() {
     let v = NonNullary::Nullary;
-    let val = v as isize; //~ ERROR non-primitive cast: `NonNullary` as `isize` [E0605]
+    let val = v as isize;
+    //~^ ERROR non-primitive cast: `NonNullary` as `isize` [E0605]
+    //~| HELP consider using the `From` trait instead
 }

tests/ui/cast/cast-enum-to-primitive-error.stderr

@@ -1,5 +1,5 @@
 error[E0605]: non-primitive cast: `NonNullary` as `isize`
-  --> $DIR/tag-variant-cast-non-nullary.rs:19:15
+  --> $DIR/cast-enum-to-primitive-error.rs:24:15
    |
 LL |     let val = v as isize;
    |               ^^^^^^^^^^ an `as` expression can be used to convert enum types to numeric types only if the enum type is unit-only or field-less

tests/ui/cast/coercion-as-explicit-cast.rs

@@ -1,5 +1,7 @@
+//! This test checks that various forms of "trivial" casts and coercions
+//! can be explicitly performed using the `as` keyword without compilation errors.
+
 //@ run-pass
-// Test that all coercions can actually be done using casts (modulo the lints).
 
 #![allow(trivial_casts, trivial_numeric_casts)]
 

tests/ui/cast/coercion-as-explicit-cast.stderr

@@ -1,5 +1,5 @@
 warning: method `foo` is never used
-  --> $DIR/trivial_casts-rpass.rs:7:8
+  --> $DIR/coercion-as-explicit-cast.rs:9:8
    |
 LL | trait Foo {
    |       --- method in this trait

tests/ui/generics/generic-enum-errors.rs

@@ -1,6 +1,15 @@
-enum Quux<T> { Bar }
-//~^ ERROR: parameter `T` is never used
+//! This test checks that unused generics are rejected by compiler
 
-fn foo(c: Quux) { assert!((false)); } //~ ERROR missing generics for enum `Quux`
+enum Quux<T> {
+    //~^ ERROR: parameter `T` is never used
+    Bar,
+}
 
-fn main() { panic!(); }
+fn foo(c: Quux) {
+    //~^ ERROR missing generics for enum `Quux`
+    assert!((false));
+}
+
+fn main() {
+    panic!();
+}

tests/ui/generics/generic-enum-errors.stderr

@@ -1,26 +1,26 @@
 error[E0392]: type parameter `T` is never used
-  --> $DIR/tag-type-args.rs:1:11
+  --> $DIR/generic-enum-errors.rs:3:11
    |
-LL | enum Quux<T> { Bar }
+LL | enum Quux<T> {
    |           ^ unused type parameter
    |
    = help: consider removing `T`, referring to it in a field, or using a marker such as `PhantomData`
    = help: if you intended `T` to be a const parameter, use `const T: /* Type */` instead
 
 error[E0107]: missing generics for enum `Quux`
-  --> $DIR/tag-type-args.rs:4:11
+  --> $DIR/generic-enum-errors.rs:8:11
    |
-LL | fn foo(c: Quux) { assert!((false)); }
+LL | fn foo(c: Quux) {
    |           ^^^^ expected 1 generic argument
    |
 note: enum defined here, with 1 generic parameter: `T`
-  --> $DIR/tag-type-args.rs:1:6
+  --> $DIR/generic-enum-errors.rs:3:6
    |
-LL | enum Quux<T> { Bar }
+LL | enum Quux<T> {
    |      ^^^^ -
 help: add missing generic argument
    |
-LL | fn foo(c: Quux<T>) { assert!((false)); }
+LL | fn foo(c: Quux<T>) {
    |               +++
 
 error: aborting due to 2 previous errors

tests/ui/modules/module-super-access.rs

@@ -1,3 +1,5 @@
+//! Check path resolution using `super`
+
 //@ run-pass
 
 #![allow(dead_code)]
@@ -6,10 +8,9 @@ pub mod a {
     pub fn f() {}
     pub mod b {
         fn g() {
-            super::f();
+            super::f(); // Accessing `f` from module `a` (parent of `b`)
         }
     }
 }
 
-pub fn main() {
-}
+pub fn main() {}

tests/ui/modules/super-at-crate-root.rs

@@ -1,4 +1,6 @@
+//! Check that `super` keyword used at the crate root (top-level) results in a compilation error
+//! as there is no parent module to resolve.
+
 use super::f; //~ ERROR there are too many leading `super` keywords
 
-fn main() {
-}
+fn main() {}

tests/ui/modules/super-at-crate-root.stderr

@@ -1,5 +1,5 @@
 error[E0433]: failed to resolve: there are too many leading `super` keywords
-  --> $DIR/super-at-top-level.rs:1:5
+  --> $DIR/super-at-crate-root.rs:4:5
    |
 LL | use super::f;
    |     ^^^^^ there are too many leading `super` keywords

tests/ui/parser/syntactic-trailing-commas.rs

@@ -1,3 +1,11 @@
+//! Checks trailing commas are accepted in various places:
+//! - Generic parameters in function and struct definitions.
+//! - Function and method arguments.
+//! - Tuple and array literal expressions.
+//! - Tuple and array destructuring patterns, including those with `..`.
+//! - Enum variant declarations.
+//! - Attributes.
+
 //@ run-pass
 
 fn f<T,>(_: T,) {}

tests/ui/ptr_ops/ptr-swap-basic.rs

@@ -1,9 +1,13 @@
+//! Check the basic functionality of `std::mem::swap` to ensure it correctly
+//! exchanges the values of two mutable variables.
+
 //@ run-pass
 
 use std::mem::swap;
 
 pub fn main() {
-    let mut x = 3; let mut y = 7;
+    let mut x = 3;
+    let mut y = 7;
     swap(&mut x, &mut y);
     assert_eq!(x, 7);
     assert_eq!(y, 3);

tests/ui/ptr_ops/ptr-swap-overlapping-regions.rs

@@ -1,17 +1,17 @@
+//! Check that `std::ptr::swap` behaves correctly when the source and destination
+//! pointers refer to the same memory location, avoiding issues like overlapping `memcpy`.
+//!
+//! Regression test: <https://github.com/rust-lang/rust/issues/5041>
+
 //@ run-pass
 
 #![allow(dead_code)]
-// Issue #5041 - avoid overlapping memcpy when src and dest of a swap are the same
-
 
 use std::ptr;
 
 pub fn main() {
     let mut test = TestDescAndFn {
-        desc: TestDesc {
-            name: TestName::DynTestName("test".to_string()),
-            should_fail: false
-        },
+        desc: TestDesc { name: TestName::DynTestName("test".to_string()), should_fail: false },
         testfn: TestFn::DynTestFn(22),
     };
     do_swap(&mut test);
@@ -24,7 +24,7 @@ fn do_swap(test: &mut TestDescAndFn) {
 }
 
 pub enum TestName {
-    DynTestName(String)
+    DynTestName(String),
 }
 
 pub enum TestFn {
@@ -34,7 +34,7 @@ pub enum TestFn {
 
 pub struct TestDesc {
     name: TestName,
-    should_fail: bool
+    should_fail: bool,
 }
 
 pub struct TestDescAndFn {

tests/ui/recursion/recursion-tail-call-no-arg-leak.rs

@@ -1,7 +1,14 @@
+//! This test verifies that tail call optimization does not lead to argument slot leaks.
+//!
+//! Regression test for: <https://github.com/rust-lang/rust/issues/160>
+
 //@ run-pass
-// use of tail calls causes arg slot leaks, issue #160.
 
-fn inner(dummy: String, b: bool) { if b { return inner(dummy, false); } }
+fn inner(dummy: String, b: bool) {
+    if b {
+        return inner(dummy, false);
+    }
+}
 
 pub fn main() {
     inner("hi".to_string(), true);

tests/ui/recursion/recursion-tail-cps.rs

@@ -1,17 +1,34 @@
+//! Verify that mutually recursive functions use CPS to avoid overflowing the stack.
+
 //@ run-pass
 
-fn checktrue(rs: bool) -> bool { assert!(rs); return true; }
+fn checktrue(rs: bool) -> bool {
+    assert!(rs);
+    return true;
+}
 
-pub fn main() { let k = checktrue; evenk(42, k); oddk(45, k); }
+pub fn main() {
+    let k = checktrue;
+    evenk(42, k);
+    oddk(45, k);
+}
 
 fn evenk(n: isize, k: fn(bool) -> bool) -> bool {
     println!("evenk");
     println!("{}", n);
-    if n == 0 { return k(true); } else { return oddk(n - 1, k); }
+    if n == 0 {
+        return k(true);
+    } else {
+        return oddk(n - 1, k);
+    }
 }
 
 fn oddk(n: isize, k: fn(bool) -> bool) -> bool {
     println!("oddk");
     println!("{}", n);
-    if n == 0 { return k(false); } else { return evenk(n - 1, k); }
+    if n == 0 {
+        return k(false);
+    } else {
+        return evenk(n - 1, k);
+    }
 }

tests/ui/svh/svh-no-api-change-no-recompile.rs

@@ -1,10 +1,17 @@
+//! This test verifies that the Signature Version Hash (SVH) system correctly identifies
+//! when changes to an auxiliary crate do not affect its public API.
+//!
+//! Specifically, it checks that adding non-public items to a crate does not alter
+//! its SVH, preventing unnecessary recompilations of dependent crates.
+
 //@ run-pass
-// note that these aux-build directives must be in this order
+
+// Note that these aux-build directives must be in this order
+
 //@ aux-build:svh-a-base.rs
 //@ aux-build:svh-b.rs
 //@ aux-build:svh-a-base.rs
 
-
 extern crate a;
 extern crate b;
 

tests/ui/traits/trait-method-signature-mismatch.rs

@@ -1,10 +1,15 @@
+//! This test verifies that implementing a trait method with a signature that does not
+//! exactly match its declaration in the trait results in a compilation error.
+//! Specifically, it checks for errors when the number of parameters or the return type
+//! in the `impl` differs from the trait definition.
+
 trait Foo {
     fn foo(&mut self, x: i32, y: i32) -> i32;
 }
 
 impl Foo for i32 {
     fn foo(
-        &mut self, //~ ERROR
+        &mut self, //~ ERROR method `foo` has 2 parameters but the declaration
         x: i32,
     ) {
     }

tests/ui/traits/trait-method-signature-mismatch.stderr

@@ -1,5 +1,5 @@
 error[E0050]: method `foo` has 2 parameters but the declaration in trait `Foo::foo` has 3
-  --> $DIR/trait-method-number-parameters.rs:7:9
+  --> $DIR/trait-method-signature-mismatch.rs:12:9
    |
 LL |       fn foo(&mut self, x: i32, y: i32) -> i32;
    |              ------------------------- trait requires 3 parameters

tests/ui/traits/tryfrominterror-result-comparison.rs

@@ -1,12 +1,19 @@
+//! This test verifies that `std::num::TryFromIntError` correctly implements `PartialEq`,
+//! allowing `Result<T, TryFromIntError>` values to be compared for equality using `==`.
+//! It specifically checks a successful numeric conversion scenario where the `Result::Ok`
+//! variant is compared, ensuring that the comparison yields the expected boolean result.
+
 //@ run-pass
 
-#![allow(unused_must_use)]
+#![allow(unused_must_use)] // Allow ignoring the result of the comparison for the test's purpose
 
 use std::convert::TryFrom;
 use std::num::TryFromIntError;
 
 fn main() {
     let x: u32 = 125;
+    // Attempt to convert u32 to u8, which should succeed as 125 fits in u8.
     let y: Result<u8, TryFromIntError> = u8::try_from(x);
+    // Verify that the Result can be correctly compared with an Ok value.
     y == Ok(125);
 }